DESCRIPTION: The intermediate filaments that define epithelial cells are composed of obligate heteropolymers of keratin molecules in a 1:1 ration. Each of roughly 30 keratins is encoded by a distinct gene, and the members have been grouped into type I and type II keratins, based on charge and other molecular relationships. A given type I keratin will pair with a type II keratin to form the heteropolymers that form keratin filaments. Epidermal keratins are differentiation specific, such that in basal layer, K5 (type II) pairs with K14 (type I), while in suprabasilar layers, K1 (II) pairs with K10 (I). During hyperproliferation and regeneration, expression of K1 and K10 is superseded by production of K6 and K16. Normally, such genes are only expressed in appendageal epidermis, but during wound healing or psoriasis, expression can be observed throughout interfollicular epidermis. The role of keratins 5, 14, 1, and 10, and the intermediate filaments that they form, in maintaining the integrity of epidermis is well established. Two autosomal dominantly inherited diseases, epidermolysis bullosa simplex (EBS) and epidermolytic hyperkeratosis, result from mutations in basal (K5.14) and suprabasal (K1/K10) keratins, respectively. It is likely that K6/16 intermediate filament function is related to cellular integrity as well. Recently, the principal investigator and coworkers, as well as other laboratories, have determined that there are multiple isoforms of K6, at least several of which are encoded by distinct genes. The overall hypothesis of this proposal is that different K6 isoforms may have distinct functions and that, as such, they would be predicted to be expressed differently in situ (in both health and disease) and be induced differently by stimuli. By extension to what has been learned about keratin mutations and human disease, the principal investigator predicts that mutations in K6 genes may exist in man and may cause phenotypes not incompatible with life. In four aims, the principal investigator proposes to: (1) Characterize the pattern of expression of K6 isoforms in human tissue; (2) determine whether there are functional differences among K6 isoforms at the protein level in vitro; (3) make transgenic mice expressing dominant negative versions of K6 isoforms; and (4) develop a new expression vector based on regulatory sequences of K6 such that expression is obligately inducible.